Apparatus for use in spinal interbody fusion

ABSTRACT

An expandable interbody fusion device includes superior and inferior endplates that are configured to receive a sequentially inserted stack of expansion members or wafers in interlocking engagement. The expansion members are formed to each have a generally U-shaped rearward facing opening. The superior and inferior endplates have openings through their outer surfaces in at least partial alignment and communication with the rearward facing openings of the expansion members. The inferior endplate has a fully bounded cavity for telescoping receipt of the superior endplate. The inferior endplate also has a fully bounded channel extending through the rear endwall thereof in direct communication with the rearward facing opening of at least one expansion member for the receipt of bone graft material into the device to promote fusion between opposing vertebral bodies of the spine.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 14/550,258, filed Nov. 21, 2014, now U.S. Pat. No. 9,517,141, whichis a divisional application of U.S. application Ser. No. 13/795,054,filed Mar. 12, 2013, now U.S. Pat. No. 8,900,312, the entire contents ofwhich are incorporated by reference herein.

FIELD OF THE INVENTION

The subject invention relates generally to the field of spinal implantsand more particularly to expandable interbody fusion devices with graftchambers.

BACKGROUND OF THE INVENTION

Spinal implants such as interbody fusion devices are used to treatdegenerative disc disease and other damages or defects in the spinaldisc between adjacent vertebrae. The disc may be herniated or sufferingfrom a variety of degenerative conditions, such that the anatomicalfunction of the spinal disc is disrupted. Most prevalent surgicaltreatment for these conditions is to fuse the two vertebrae surroundingthe affected disc. In most cases, the entire disc will be removed,except for a portion of the annulus, by way of a discectomy procedure. Aspinal fusion device is then introduced into the intradiscal space andsuitable bone graft or bone substitute material is placed substantiallyin and/or adjacent the device in order to promote fusion between twoadjacent vertebrae.

Certain spinal devices for achieving fusion are also expandable so as tocorrect disc height between the adjacent vertebrae. Examples ofexpandable interbody fusion devices are described in U.S. Pat. No.6,595,998 entitled “Tissue Distraction Device”, which issued on Jul. 22,2003 (the '998 patent), U.S. Pat. No. 7,931,688 entitled “ExpandableInterbody Fusion Device”, which issued on Apr. 26, 2011 (the '688patent), and U.S. Pat. No. 7,967,867 entitled “Expandable InterbodyFusion Device”, which issued on Jun. 28, 2011 (the '867 patent). The'998 patent, the '688 patent and the '867 patent each disclosessequentially introducing in situ a series of elongate inserts referredto as wafers in a percutaneous approach to incrementally distractopposing vertebral bodies to stabilize the spine and correct spinalheight, the wafers including features that allow adjacent wafers tointerlock in multiple degrees of freedom. The '998 patent, the '688patent and the '867 patent are assigned to the same assignee as thepresent invention, the disclosures of these patents being incorporatedherein by reference in their entirety.

Certain interbody fusion devices also include hollow portions orchambers that are filled with suitable material such as bone graft topromote fusion between vertebral bodies. The extent and size of thechambers establish areas of contact that are configured so as to assuremaximum contact between the bone graft and the vertebral bodies.Sufficient surface area of the device surrounding the chambers needs tobe maintained in order to provide an appropriate load bearing surface towithstand the compressive forces exerted by the opposing vertebralbodies. In addition, where expandable interbody fusion devices are usedto correct height within the intradiscal space, the effect of shearforces on the expanded device due to torsional movement of the spinealso needs to be considered.

Accordingly, there is a need to develop expandable interbody fusiondevices with bone graft chambers that take into account and balancethese factors, as well as to facilitate the introduction of bone graftinto the device and through the graft chambers once expanded.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved expandabledevice with openings serving as bone graft chambers for implantationinto the intradiscal space between two opposing vertebral bodies of aspine having the facility for introducing bone graft thereinto uponexpansion.

DESCRIPTION OF THE FIGURES

FIG. 1 is front perspective view of an expandable interbody fusiondevice in unexpanded condition in accordance with one embodiment of thepresent invention.

FIG. 2 is a perspective cross sectional view of the unexpanded device ofFIG. 1 as seen along viewing lines II-II of FIG. 1.

FIG. 3 is a rear perspective view of the device of FIG. 1.

FIG. 4 is a top perspective view of an interlocking wafer serving as anexpansion member to expand the interbody fusion device of FIG. 1.

FIG. 5 is a bottom perspective view of the interlocking wafer shown inFIG. 4.

FIG. 6 is front perspective view of the expandable interbody fusiondevice FIG. 1 expanded to an expanded condition.

FIG. 7 is a perspective cross sectional view of the expanded device ofFIG. 6 is seen along viewing lines VI-VI of FIG. 6.

FIG. 8 is a top perspective view of an inserter for inserting wafersreleasably connected to the unexpanded device of FIG. 1.

FIG. 9 is longitudinal cross sectional view of the inserter of FIG. 8.

FIG. 10 is a perspective view of the guide used with the inserter ofFIG. 8 releasably connected to the expanded device of FIG. 6.

FIG. 11 is a top perspective view of an alternative lordotic expandablefusion device.

DESCRIPTION OF THE EMBODIMENTS

For the purposes of promoting and understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and described in the following written specification. It isunderstood that no limitation to the scope of the invention is therebyintended. It is further understood that the present invention includesany alterations and modifications to the illustrated embodiments andincludes further applications of the principles of the invention aswould normally occur to one skilled in the art to which this inventionpertains.

In accordance with one embodiment of the invention, an expandableinterbody fusion device 10 includes a first superior endplate 12 and asecond inferior endplate 14, as shown in FIGS. 1-3. The interbody fusiondevice 10 has a height across the superior and inferior endplates 12, 14in the unexpanded condition as illustrated in FIGS. 1-3 that is lessthan the normal anatomic height of a typical intradiscal space. Theinvention contemplates that a series of expansion members, such asinterlocking wafers 100 as will be described, are introduced into thedevice 10 to distract the opposing vertebrae by separating the superiorand inferior endplates 12, 14 in situ. Insertion of the wafers 100separates the endplates 12, 14 to expand the height of the device withinthe intradiscal space and to ultimately restore the normal anatomicheight of the disc space. Expansion devices of this type are shown anddescribed in the '998 patent, the '688 patent and the '867 patentdescribed hereinabove and incorporated herein by reference.

The present invention contemplates an improved interbody fusion device10 that particularly includes openings that define graft chambers forcontainment of materials that promote bone fusion through the devicebetween opposing vertebral bodies.

The superior endplate 12 as shown in FIGS. 1-3 and 6-7 is elongate andcomprises a hub 16 having pair of side surfaces 18 and 20 extendinglongitudinally on each side of the hub 16 and a pair of end surfaces 22and 24 extending respectively at the proximal rear end and the distalfront end of the superior endplate 12. The hub 16 is sized andconfigured to fit within a cavity of the inferior endplate 14 fortelescoping movement therewithin, as will be described. The lowersurface 26 of the hub 16 (FIG. 2) includes a shaped configurationdefined by wafer mating features 28 that are substantially identical tothe mating features on the lower surface of each wafer 100, as will bedescribed. The hub 16 defines a series of grooves 30 as shown in FIG. 6extending along each side surface 18 and 20 thereof that is configuredto engage ribs (not shown) projecting interiorly of the inferiorendplate 14. This engagement temporarily holds the superior and inferiorendplates together in the expansion direction as the device 10 isintroduced into the intradiscal space to be distracted.

As shown particularly in FIGS. 1-3 and 6-7, the superior endplate 12includes a graft chamber defined by an opening 32 extending through theupper outer surface 12 a and the lower surface 26. In a particulararrangement, the opening 32 is situated to lie more adjacent to theproximal surface 20 or rear end of the device 10. In accordance with onearrangement, the superior endplate 12 is formed of a biocompatiblepolymer such as polyethylethylketone (PEEK). PEEK is used in fusionapplications for its combination of strength, biocompatibility, andelasticity which is similar to human bone. Other composites may includederivatives of PEEK such as carbon fiber reinforced PEEK and PEKK,respectively. In a particular aspect, the superior endplate 12 mayfurther include an upper endcap 34 that defines the outer surface 12 a.Endcap 34 may be a separate plate formed of material for the promotionof bone growth, such as titanium, and may be attached to the endplate 12with suitable conventional techniques. As an alternative, the uppersurface 12 a may be defined by a coating of a suitable layer of bonegrowth promotion material, such as titanium, which may be deposited byconventional techniques such as, for example, by ion implantation asdescribed in U.S. Pat. No. 4,743,493, entitled “Ion Implantation ofPlastics”, issued on May 10, 1988 to Sioshansi et al., the contents ofwhich are incorporated by reference herein.

The inferior endplate 14 of the interbody fusion device 10 as shown inFIGS. 1-3 and 6-7 is elongate and comprises a pair of opposing spacedapart sidewalls 36 and 38 extending along the longitudinal direction andprojecting upwardly from the lower outer surface 14 a. A pair of spacedapart endwalls 40 and 42 extend laterally across the device and projectupwardly from outer surface 14 a. Rear end wall 40 is disposed at therear or proximal end of the device 10 and front end wall 42 is disposedat the front or distal end of the device 10. The side walls 36, 38together with rear end wall 40 and front end wall 42 form an open,upwardly facing fully bounded interior cavity 44 as shown in FIGS. 1-2and 7. The interior cavity 44 is sized and configured to receive thesuperior endplate 12 including the hub 16 and the endcap 34 inrelatively close fit between the side walls 36 and 38 and the end walls40 and 42 of the inferior endplate 14 in a non-expanded condition asshown in FIGS. 1 and 2. The hub 16 of superior endplate 12 remains fullycontained within the inferior endplate 14 during telescoping expansionof the device 10 as shown in FIGS. 6 and 7, contributing to thetorsional strength of the expanded device 10.

The inferior plate 14 as shown in FIG. 3 defines a fully bounded waferchannel 46 extending through the rear endwall 40 in communication withinterior cavity 44 and through which the wafers 100 which serve asexpansion members are introduced. The inferior endplate 14 includes apair of opposite ledges 48 that define an upper support surface on whicheach wafer 100 is supported as it introduced into the wafer channel 46,as will be described. The ledges 48 define the bottom surface of thecavity 44. Wafers are introduced sequentially into wafer channel 46, aswill be described. The rear endwall 40 further defines a threadedconnection opening 50 for threaded releasable receipt of a guide pin foruse in the introduction of wafers 100 and in the delivery of bone graftmaterial into the device 10, as will also be described. Rear endwall 40may also additionally include a pair of bilateral notches 52 adjacentthe sidewalls 36 and 38 for use in attachment to portions of the waferinserter for the establishment of a rigid connection to the device 10for insertion into the intradiscal space.

As shown particularly in FIGS. 1-3 and 6-7, the inferior endplate 14includes a graft chamber defined by an opening 54 extending through thelower outer surface 14 a and the upper support surface 48 incommunication with cavity 44. In a particular arrangement, the opening54 is situated to lie more adjacent to the proximal surface 20 or rearend of the device 10 and at least in partial alignment with the opening32 in superior endplate 12. In accordance with one arrangement, theinferior endplate 12 is formed of a material different from the materialof the superior endplate 12. In this aspect, the inferior endplate 12may be formed of a biocompatible metal, such as titanium, for itsstrength properties. Titanium is chosen for strength, biocompatibility,processing capability, and fluoroscopic imaging properties(radiolucency). Other alternative materials include cobalt chrome,stainless steel (both stronger than titanium but much less radiolucent),or biocompatible ceramics such as silicon nitride or zirconia, which areradiolucent. Titanium and silicon nitride have demonstrated goodapposition to bone and superior to PEEK. In this regard where inferiorendplate 14 is formed of titanium, the lower outer surface 14 a wouldprovide for the promotion of bone growth. Where inferior endplate 14 isnot formed of a bone growth promotion material, lower outer surface 14 amay be coated with a suitable layer of bone growth promotion material,such as titanium, and deposited in a conventional manner as describedhereinabove.

Where inferior endplate 14 is formed of titanium or other suitable metalthat is radiopaque, windows 56 may be formed through sidewalls 36 and 38and/or through front endwall 42 as shown in FIGS. 1-3 and 6-7 so as toallow visual observation of the expansion of the device 10 uponinsertion of the wafers 100 by suitable imaging techniques, such asfluoroscopy.

Details of an interlocking wafer 100 are shown in FIGS. 4-5. The wafer100 is elongate and has an upper surface 102 and a lower surface 104,both of which are generally planar so that the wafers can form a stablestack within the interbody fusion device 10. Wafer 100 includes atrailing rear end 106 and a leading front end 108. The rear end 106 isformed substantially in the form of a horseshoe, with a pair of spacedopposing arms 112 and 114 defining an open rearward facing generallyU-shaped opening 116. The surface 118 between the upper surface 102 andthe lower surface 104 at the base of opening 116 defines a pushingsurface, as will be described. The opening 116 at the rear end of eachwafer 100 is provided to allow bone graft material to flow into thedevice 10 through the openings 116 and into the openings 32 and 54extending through the superior endplate 12 and the inferior endplate 14,respectively.

The rear end 106 includes a downward-facing sloped surface 120 at thefree end of each arm 112 and 114 that corresponds angularly to anupward-facing surface 122 on the leading front end 108 of the wafer 100.The sloped surfaces help displace an earlier inserted wafer 100 uponintroduction of a new wafer. More specifically, when a first wafer 100 ais introduced through the wafer channel 46, resting on the ledges 48,the downward-facing sloped surface 120 thereof is lifted upon contactwith the upward-facing slope 122 of a newly inserted wafer 100 b (FIG.7). This allows the newly inserted wafer to ride along the ledges 48until it is positioned fully underneath the previous wafer as more fullydescribed in the '867 patent.

The wafer 100 includes several features for interlocking engagement tothe hub 16 and to adjacent wafers 100 in a complementary interlockingmating interface. One particular feature includes a series of lockingelements defined by resiliently deflectable prongs 124 that projectoutwardly above the upper surface 102 of the wafer 100 in the directionof expansion of device 10. A complementary series of locking surfaces126 are defined in the lower surface 104 of the wafer 100 for resilientengagement with the prongs 124 as wafers are inserted into device 10 toform a stack. It should be appreciated that the prongs 124 andassociated locking surfaces 126 may be formed on either the uppersurface or the lower surface of a wafer 100 as desired. The lowersurface 104 of each wafer 100 as shown in FIGS. 5 and 7 also defines aT-slot configuration 128 for mating with a T-bar configuration 130 onthe upper surface 102 of a successive wafer 100 as shown in FIGS. 4 and7. It should be appreciated that the respective T-bar and T-slotconfigurations may also be formed on either the upper surface or thelower surface of a wafer 100 as desired. In the illustrated arrangement,there are two prongs 124 extending generally linearly and substantiallycentrally along the elongate longitudinal direction adjacent the frontend 108 of wafer 100. The structure and function of a wafer 100 and theprongs 124 are more fully described in the '867 patent, incorporatedherein by reference.

The superior and inferior endplates 12 and 14 are configured to beinitially releasably engaged by the ribs (not shown) and the grooves 30when the device 10 is unexpanded, as shown in FIGS. 1 and 2. In thisunexpanded condition, the device 10 is attached to an inserter 200 asshown in FIGS. 8 and 9. In this stage, the hub 16 is disposed within thecavity 44 of inferior endplate 14 with the ribs (not shown) on theinterior surfaces of side walls 36, 38 engaging the grooves 30 extendingalong each side of the hub 16. The lower surface 26 of hub 16 is on orclosely adjacent to the wafer support ledges 48 in facing relationship.This engagement temporarily holds the superior and inferior endplatestogether as the device 10 is introduced into the intradiscal space to bedistracted. In this unexpanded condition the outer surface 12 a of thesuperior endplate 12 is substantially flush with the upper surfaces ofthe sidewalls 36 and 38 as illustrated in FIGS. 1 and 2. In addition toproviding strength for the device 10 as described hereinabove, suchnesting of the superior endplate 12 within inferior endplate 14 allowsfor lower height of the unexpanded device 10.

The inserter 200 as illustrated in FIGS. 8 and 9 comprises a trackassembly 202 and a handle 204 for individually sequentially inserting aplurality of wafers 100 supported linearly within the track assembly202. A source of wafers 100 is provided in a cartridge 206 supported bythe track assembly 202. A pair of opposing fingers 208 is provided atthe distal end of the track assembly 202, fingers 208 releasablyengaging the notches 52 in the rear endwall 40 for connection thereto.As depicted particularly in FIG. 9, the track assembly 202 supports anelongate guide pin 210 the distal end 210 a of which is threaded forreleasable threaded connection with threaded opening 50 in rear endwall40 of the device 10. Inserter 200 comprises an elongate driver 212 thatis translatably supported within the track assembly 202, the distal endof which is configured to enter the rearward facing opening 116 of eachwafer 100 and engage the pushing surface 118. Upon actuation of thehandle and translation of the driver 212, the wafer 100 is suitablymoved through the channel 46 and into the device 10 by the force of thedistal end of the driver 212 against the pushing surface 118. Inserter200 further includes a quick disconnect member 214 which upon rotationallows the inserter 200 to be detached from the guide pin 210, therebyleaving the guide pin 210 releasably connected to the expanded device 10after suitable insertion of the desired number of wafers, as shown inFIG. 10. With the guide pin 210 attached to the device 10 at opening 50,the channel 46 extending through the rear end wall 40 of device 10 isfully exposed and may be used for the introduction of suitable bonegraft material into expanded device 10. For the introduction of a bonegraft material, the guide pin 210 may be used as a locator forsubsequent attachment to an apparatus containing such bone graftmaterial whereby such apparatus may be supported by the guide pin 210while allowing access into channel 46. Further details of the structureand operation of the inserter 200 are described in commonly assignedU.S. Pat. No. 6,997,929, entitled “Tissue Distraction Device”, andissued Feb. 14, 2006, the contents of which are incorporated byreference herein.

The manner in which the interbody fusion device 10 is expanded isillustrated in FIGS. 6-7. When the first wafer 100 is introduced, theinterlocking features on the upper surface 102 of the wafer 100 engagethe mating features 28 on the lower surface 26 of superior endplate 12lifting the superior endplate 12 upwardly within the cavity 44 betweensidewalls 36, 38 and breaking the initial releasable engagement. Whenthe first inserted wafer 100 is introduced into the device 10 therearward facing opening 116 in the wafer 100 is located to be in atleast partial alignment and communication with the openings 32 and 54extending through the superior endplate 12 and inferior endplate 14,respectively. This process continues with each successive wafer 100inserted beneath a previously inserted wafer 100 until a complete stackis formed telescopically lifting the superior endplate 12 relative tothe inferior endplate 14, as depicted in FIG. 7. As each subsequentwafer 100 is introduced, the prongs 124 lockingly engage the matinglocking surfaces 126 features on the lower surfaces of each previouslyintroduced wafer 100, with the openings 116 of each wafer 100 beingdisposed such that they are in at least partial alignment andcommunication with the openings 116 of each previously introduced wafer100. The lowermost wafer 100 is supported on the support surfaces ofledges 48 with the rearward facing opening being in direct communicationwith the channel 46 extending through rear endwall 40 of inferiorendplate 14. It should be noted that all the wafers 100 are containedwithin and constricted by the opposing side walls 36, 38 and the rearand front end walls 40, 42 so as to provide additional resistanceagainst torsional movement of the spine. The inserter 200 is releasedfrom the expanded interbody fusion device 10 upon unthreading the guidepin 210 from opening 50.

Having described the interbody fusion device 10, a suitable bone filleror bone graft to promote fusion between opposing vertebral bodies may beinserted into the expanded device 10 as well as into the intradiscalspace adjacent to device 10. With the inserter 200 used to insertinserts such as wafers 100 into device 10 having been removed from theexpanded device 10, it can be appreciated that the wafer insertionchannel 46 provides clear and unobstructed access into the expandeddevice 10 and into the rearward facing openings 116 of wafers 100,facilitating the introduction of bone graft material. A suitable graftinsertion instrument using the guide pin 210 as a locator may be used toinject bone graft under pressure into the expanded device 10. Under anappropriate pressure, such bone graft will flow through into channel andopenings 116 and into the openings 32 and 56 of superior endplate 12 andinferior endplate 14. Injection of the bone graft will continue untilthe graft is stress loaded against the endplates of the opposingvertebral bodies. In some instances, bone graft may be pre-loaded intoan unexpanded device 10 prior to insertion of the device 10 into theintradiscal disc space. Suitable bone graft materials may includeautograph bone, allograft bone, bone morphogenic protein (BMP) andxenograft and synthetic derived bone substitutes, as described forexample, in the '998 patent. It should also be understood that amaterial with a bone fusion promoting substance, such as a spongesaturated with BMP, may be placed in the openings 32 and 54 suitablyformed to support such a sponge. This will allow the fusion promotingsubstance to be pre-loaded into device 10 and not be disrupted uponexpansion of device 10 by insertion of wafers 100 as described herein.

It is contemplated that the wafers 100 described herein, be formed of abiocompatible material that is sufficiently rigid to form a solid stackas the successive wafers are inserted into the device. Thus, in onespecific embodiment, the wafers 100 are formed of PEEK or a carbon-fiberreinforced PEEK, or similar polymeric material.

In accordance with certain specific applications, the overall length ofthe device 10 as shown in FIGS. 1 and 6, as defined by the length of theinferior endplate 14, is about 25 mm. The width of the device isapproximately 9 mm. The height of the unexpanded device 10 of FIGS. 1-2with the superior endplate 12 fully nested within the inferior endplate14 is approximately 7 mm. With the introduction of five wafers 100, eachof which has a thickness of approximately 1.0 mm, the height of device10 may be expanded from an unexpanded height of approximately 7 mm to anexpanded height of approximately 12 mm. Of course, the number of wafersmay vary depending upon the particular surgery and the initial heightmay also be different. For example, device 10 may be formed to have aninitial unexpanded height of approximately 9 mm and with the addition ofseven wafers 100, each having a thickness of 1 mm, the height of device10 may be increased to approximately 16 mm. As such, it should beappreciated that these dimensions are only illustrative and that thedimensions of the device 10 and the number of wafers 100 to be insertedand their thicknesses may vary depending upon the application.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same should be considered asillustrative and not restrictive in character. It is understood thatonly the preferred embodiments have been presented and that all changes,modifications and further applications that come within the spirit ofthe invention are desired to be protected. For instance, as shown inFIG. 11, a device 300 embodying the features described herein may beformed to have a lordotic shape, whereby the leading front end 310intended to be placed in the anterior portion of the intradiscal spacemay have a height greater than the trailing rear end 320, intended to beplaced in the posterior portion of the intradiscal space.

What is claimed is:
 1. An apparatus for use in spinal interbody fusion,comprising: an expandable device including a first outer surface forcontacting one vertebral body in a spine and a second outer surface forcontacting a second opposing vertebral body in said spine, a front endand a rear end, and a channel extending into said expandable device; aninserter releasably attached to said expandable device at said rear end,said inserter including a track assembly having a distal end and aproximal end; and a guide pin releasably connected to said expandabledevice and detachably connected to said inserter, said guide pin beingsupported by said track assembly and being detachable therefrom, saidguide pin remaining releasably connected to said expandable device upondetachment of said inserter from said expandable device and said guidepin, said guide pin being configured to serve as a locator forsubsequent attachment to another apparatus, including an apparatus forintroducing bone graft material into said expandable device through saidchannel.
 2. The apparatus of claim 1, wherein said expandable devicecomprises a first opening through said first outer surface and a secondopening through said second outer surface, said channel communicatingwith said first opening and said second opening, said guide pin beingreleasably connected to said expandable device at a location spaced fromsaid channel.
 3. The apparatus of claim 2, wherein said expandabledevice comprises a first endplate defining said first outer surface andsaid first opening therethrough, and a second endplate defining saidsecond outer surface and said second opening therethrough, said firstendplate and said second endplate being movable relative to each otherin an expansion direction.
 4. The apparatus of claim 2, wherein saidchannel extends through said rear end of said expandable device.
 5. Theapparatus of claim 2, wherein said rear end of said expandable deviceincludes an attachment surface for releasable attachment of saidinserter.
 6. The apparatus of claim 5, wherein said attachment surfaceincludes at least one notch adjacent the rear end of said secondendplate.
 7. The apparatus of claim 6, wherein said inserter includes adistal end comprising at least one finger releasably engaged in said atleast one notch.
 8. The apparatus of claim 5, wherein said guide pin iselongate having a distal end and a proximal end, the distal end having athreaded extent, and wherein said attachment surface includes a threadedopening in receipt of said threaded extent of said guide pin.
 9. Theapparatus of claim 1, wherein said inserter includes a rotatable quickdisconnect member at the proximal end of said track assembly forallowing said track assembly to be detached from said guide pin whilesaid guide pin remains releasably connected to said rear end of saidsecond endplate.
 10. The apparatus of claim 1, wherein said insertersupports a plurality of inserts for sequential insertion into saidchannel, one beneath the other, each of said inserts having a rearwardfacing opening and a pushing surface engaged by a driver of saidinserter to insert said inserts into said expandable device.
 11. Theapparatus of claim 1, wherein said track assembly supports at least oneinsert for insertion into said expandable device through said channelthrough the rear end of said expandable device for causing expansion ofsaid expandable device.
 12. The apparatus of claim 11, wherein saidtrack assembly further comprises an elongate driver translatably movablethereon, said driver having a distal end and a proximal end, the distalend being configured to engage said insert and drive said insert intosaid expandable device through said channel.
 13. The apparatus of claim12, wherein said insert comprises an elongate body having a front end, arear end, and a rearward facing opening defining a U-shaped opening, abase of said opening defining a pushing surface.
 14. The apparatus ofclaim 13, wherein said driver is sized and configured to enter saidU-shaped opening of said insert and engage said pushing surface of saidinsert.
 15. The apparatus of claim 11, wherein said inserter includes anactuator attached to said track assembly and operable to translatablymove said insert into said expandable device while said guide pin isconnected to said expandable device.